[v6.6] KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0a40c6fbd105 Linux 6.6.141
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15d922f2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=7ec52ddfdce5ed52df60
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bef5f7e53495/disk-0a40c6fb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/61ce39aaab25/vmlinux-0a40c6fb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/43d2363e7871/bzImage-0a40c6fb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7ec52d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in l2cap_sock_new_connection_cb+0x208/0x2b0 net/bluetooth/l2cap_sock.c:1494
Read of size 8 at addr ffff88805f8c3548 by task kworker/u5:1/12194

CPU: 0 PID: 12194 Comm: kworker/u5:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: hci4 hci_rx_work
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
l2cap_sock_new_connection_cb+0x208/0x2b0 net/bluetooth/l2cap_sock.c:1494
l2cap_connect_cfm+0x375/0x1070 net/bluetooth/l2cap_core.c:7333
hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:1999
le_conn_complete_evt+0xfdc/0x1540 net/bluetooth/hci_event.c:5793
hci_le_conn_complete_evt+0x187/0x440 net/bluetooth/hci_event.c:5819
hci_event_func net/bluetooth/hci_event.c:7491 [inline]
hci_event_packet+0x7ba/0x1270 net/bluetooth/hci_event.c:7546
hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4018
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>

Allocated by task 12194:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slab_common.c:1007 [inline]
__kmalloc+0xb4/0x230 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
sk_prot_alloc+0xe7/0x210 net/core/sock.c:2096
sk_alloc+0x3a/0x360 net/core/sock.c:2152
bt_sock_alloc+0x3b/0x310 net/bluetooth/af_bluetooth.c:148
l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1900 [inline]
l2cap_sock_new_connection_cb+0xf1/0x2b0 net/bluetooth/l2cap_sock.c:1479
l2cap_connect_cfm+0x375/0x1070 net/bluetooth/l2cap_core.c:7333
hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:1999
le_conn_complete_evt+0xfdc/0x1540 net/bluetooth/hci_event.c:5793
hci_le_conn_complete_evt+0x187/0x440 net/bluetooth/hci_event.c:5819
hci_event_func net/bluetooth/hci_event.c:7491 [inline]
hci_event_packet+0x7ba/0x1270 net/bluetooth/hci_event.c:7546
hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4018
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Freed by task 16498:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
__kmem_cache_free+0xba/0x1e0 mm/slub.c:3843
sk_prot_free net/core/sock.c:2135 [inline]
__sk_destruct+0x4e0/0x660 net/core/sock.c:2230
l2cap_sock_cleanup_listen+0xda/0x3e0 net/bluetooth/l2cap_sock.c:1456
l2cap_sock_release+0x6a/0x1e0 net/bluetooth/l2cap_sock.c:1417
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1420
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1d4/0x260 kernel/task_work.c:245
get_signal+0x1235/0x13f0 kernel/signal.c:2678
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2721 [inline]
call_rcu+0x153/0x950 kernel/rcu/tree.c:2837
netlink_release+0x1702/0x1ad0 net/netlink/af_netlink.c:801
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1420
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1d4/0x260 kernel/task_work.c:245
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Second to last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2721 [inline]
call_rcu+0x153/0x950 kernel/rcu/tree.c:2837
netlink_release+0x1702/0x1ad0 net/netlink/af_netlink.c:801
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1420
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1d4/0x260 kernel/task_work.c:245
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x95a/0x2460 kernel/exit.c:884
do_group_exit+0x21b/0x2d0 kernel/exit.c:1026
get_signal+0x12fc/0x13f0 kernel/signal.c:2902
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
irqentry_exit_to_user_mode+0x9/0x30 kernel/entry/common.c:315
exc_page_fault+0x8c/0x100 arch/x86/mm/fault.c:1519
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608

The buggy address belongs to the object at ffff88805f8c3000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1352 bytes inside of
freed 2048-byte region [ffff88805f8c3000, ffff88805f8c3800)

The buggy address belongs to the physical page:
page:ffffea00017e3000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5f8c0
head:ffffea00017e3000 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c42000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5770, tgid 5770 (syz-executor), ts 67327310099, free_ts 16736551053
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
prep_new_page mm/page_alloc.c:1588 [inline]
get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
alloc_slab_page+0x5d/0x160 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
__kmem_cache_alloc_node+0x19e/0x250 mm/slub.c:3534
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc+0xa4/0x230 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
kzalloc include/linux/slab.h:721 [inline]
ops_init+0x8b/0x640 net/core/net_namespace.c:129
setup_net+0x3b6/0xa30 net/core/net_namespace.c:343
copy_net_ns+0x36d/0x5e0 net/core/net_namespace.c:520
create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:228
ksys_unshare+0x4f5/0x8c0 kernel/fork.c:3442
__do_sys_unshare kernel/fork.c:3516 [inline]
__se_sys_unshare kernel/fork.c:3514 [inline]
__x64_sys_unshare+0x38/0x40 kernel/fork.c:3514
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1181 [inline]
free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
free_contig_range+0xa1/0x150 mm/page_alloc.c:6420
destroy_args+0x80/0x850 mm/debug_vm_pgtable.c:1015
debug_vm_pgtable+0x411/0x440 mm/debug_vm_pgtable.c:1400
do_one_initcall+0x242/0x790 init/main.c:1249
do_initcall_level+0x137/0x1f0 init/main.c:1311
do_initcalls+0x69/0xd0 init/main.c:1327
kernel_init_freeable+0x3ed/0x580 init/main.c:1564
kernel_init+0x1d/0x1c0 init/main.c:1454
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
ffff88805f8c3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805f8c3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805f8c3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805f8c3580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805f8c3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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